Classical Nordic Music Lontano Riverside Studios Nash Ensemble SBC, Lon don

Programme-note writers beware: don't tell critics too much. Mentally casting around, trying to work out why I had lingering doubts about the Icelandic composer Karolina Eiriksdottir's opera I Have Seen Someone, I read in my booklet that the libretto was adapted from a collection of poems. Suddenly it was all too clear: this wasn't so much a plot as a series of meditations on a plot, sparsely staged - the theme: love, illness, loss and the possibility of a new beginning.

Why the problem? Because, however excellently the two protagonists (soprano Sarah Leonard and baritone Mark Oldfield) sang and enunciated, and however discreetly Lontano played for its conductor Odaline de la Martinez, only about a third of the text was comprehensible - even in the relatively intimate space of Riverside Studio 2. To get the most out of the work we needed a printed text, or at least something more detailed than just a one-and-a-half-line synopsis.

It says a lot for Eiriksdottir's music that much of it managed to impress even when its dramatic function was unclear. But when it was clear what was happening, and what the characters were expressing, the impact was far deeper. The hospital sequence, which took us inside the minds of the woman and her dying lover, was a fine sustained crescendo of anxiety, the moment of death registered by the orchestra with telling simplicity. In the later grieving scenes there were more shafts of compassionate but realistic insight.

But so much depended on one's being able to hear music and words. Is there a conflict of intentions here? Is I Have Seen Someone poised uncomfortably between opera and song-cycle? Perhaps concert performance would work better, or maybe the natural medium is television. Whatever, I Have Seen Someone deserves another chance.

Further down the Thames, on the South Bank, the Nash Ensemble has been pursuing its own 20th-century music series in the Purcell Room and, by avoiding the obvious big names, has managed to work the odd refreshing surprise. Rupert Bawden's characterful, elegantly crafted The Donkey Dances (5 March) was one such, as was the rediscovery of De Falla's exquisite Psyche, for voice, flute, harp and string trio.

Then, last Tuesday, the Nash too turned northwards: works by the Norwegian Arne Nordheim, the Swede Jan Sandstrom and the Dane Anders Nordentoft. Nordheim's Partita for Paul [Klee] was a suite of gritty solo violin pieces, grittily played by Krysia Osostowicz, the landscape of the last two opening out magically with the help of two discreetly placed loudspeakers and a digital relay unit. Nordentoft's Hymne contrasted what its composer called "vigorous masculine" and "feminine... softly rocking" ideas. I found the "feminine" Nordentoft more convincing, especially in the sweetly scored harmonies of the coda.

Sandstrom's Wahlberg Variations, for trombone and chamber ensemble, was a tribute to the eccentric Swedish painter Ulf Wahlberg. The vivid humour of Sandstrom's hugely enjoyable Trombone Concerto was there (and who better than trombonist Christian Lindberg to bring it out?), but it was patchier and more thinly spread. What a contrast it made with the brilliance and delicious wit of Stravinsky's Octet, flautist Philippa Davies and clarinettist Michael Collins setting the tone to perfection. That's the way to end a concert.

STEPHEN JOHNSON